Chamber sealing apparatus for web materials



Dec. 6, 1960 P. ALEXANDER CHAMBER smunc APPARATUS FOR was MATERIALS Filed Sept. 16, 1957 5 Sheets-Sheet 1 m R N v E w, |.T in mm mm M V//////////// 222i 6 m I JM 3 mm mm 9?... H I U E l I 2.. 5 m 0% I I 2 S v ww E. r M A @m m ow 3. m m .OE .5 on a on m 8 mm m 3 2 Ma Ma 8 wu 8 n B 9 o 02 6. o e fi a m 2 4/ mu 8 v. e 7 AI 2 a N2 n2 2 2 n 2 ATTORNEYS Dec. 6, 1960 P. ALEXANDER CHAMBER SEALING APPARATUS FOR WEB MATERIALS 5 Sheets-Sheet 2 Filed Sept. 16, 1957 O R m M L w w 9. mm

m mwmm 2 N A BY M, 1 6. V ar-t,

ATTORNEYS Dec? 9 P. ALEXANDER 2,963,001

CHAMBER SEALING APPARATUS FOR WEB MATERIALS Filid Sept. 16, 1957 5 She'ets-Sheet 3 FlG.5

INVENTOR PAUL. ALEXANDER ATTORNEYS Dec. 6, 1960 P. ALEXANDER CHAMBER SEALING APPARATUS FOR WEB MATERIALS 5 Sheets-Sheet 4 INVENTQR PAUL ALEXANDER m Zv/////////////%//////W///////////////////////// mm O E v oi 0 do 0 o o .s

IY D I 5 as 2,963,001 CHAMBER SEALING APPARATUS FOR WEB MATERIALS Filed Sept. 16, 1957 P. ALEXANDER Dec. 6, 1960 5 Sheets-Sheet 5 2.9m ed. M

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United States Patent CHAMBER SEALING APPARATUS FOR WEB MATERIALS Paul Alexander, Princeton, N.J., assignor to Continental Can Company, Inc., New York, N.Y., a corporation of New York Filed Sept. 16, 1957, Ser. No. 684,252

15 Claims. (Cl. 118-49) This invention relates to apparatus for sealing chambers at points where web materials enter or leave the same.

In treating webs of material under conditions where the atmosphere must be excluded, or treating materials prevented from existing to the atmosphere, it is a practice to employ a seal of some sort. Various structures have been proposed and used, but have not been satisfactory under conditions where a minimum flow of gas is requisite and where the web material is subject to change, e.g. of dimension, during its travel through the treating chamber.

As an example, when a vacuum chamber is to be employed for deposition of vaporized metal upon a paper web, the paper shrinks in length so that in'et and outlet feeding devices must operate at different speeds, under close control, to avoid tearing of the web. The need for restricting movement of atmospheric gases into the chamber complicates the problem, because the employment of a pair of rollers above and below the web and in contact with the web surfaces, and with the roller axes opposite one another in a plane transverse to the direction of web movement, requires either a fixed spacing of the axes or a permissive movement of one or both axes relative to the web. When the axes are fixed, and the rollers contact the web surfaces for providing the maximum sealing effect, any thickening of the web material causes a binding and slowing of the web, and tearing results from the traction exerted by downstreamward pulling means: such thickening occurs, for instance, when two web lengths are joined in the usual fashion by a lap joint. When several pairs of rollers are present, all being driven, there is little automatic adjustment of length changes; and the short lengths between pairs of rollers are highly susceptible to tearing when a thickened part of the web enters the nip of an upstreamward pair of rollers while the downstreamward pairs are exerting traction on the web. When one roller has a permissive movement, to and from the web, to permit this, it is necessary to provide some means such as a gravitational mass or a spring, to return the roller toward the web when the thickening has passed: such means have a lug period so that more leakage occurs after a thickening has passed, than at other times; and the energy for moving the roller away must come from the web itself, so that again there is a longitudinal jerk and strain along the web as the thickening is endeavoring to pass. If. it is sought to alleviate this by mounting the rollers at one side of the web to move as a unit, then the energy for moving the entire mass of such rollers and their frames and supports must come from the engagement of the thickened part with the first pair of rollers. In addition, such devTces usually require careful adjustments for web stocks of even minor change of normal thickness, and to compensate wear: and an adjustment which places a pressure upon the web, even by driven rolls, can cause a calendering effect which changes the surface characteristics and hence modifies the behavior during the treatment in the chamber: this is true of both coated paper stocks and stocks in which specific surface patterns are to be retained.

"ice

It has been found that the necessary attributes of low leakage along such webs, and freedom from damage to the web material, can be attained by employment of rollers whose axes are staggered at the sides of the web and which have surfaces so disposed as to permit the web, with the variations of thickness, to pass between the rollers of a pair without pinching, and with the surfaces also making contact with the two surfaces of the web so that the leakage is being restricted by the presence of the web itself. 7

An object of this invention is to provide a seal for admission or withdrawal of a web from a treating chamber, in which the web moves between the staggered rollers of a pair and in contact with both rollers but without being pinched or squeezed therebetween.

Another object is the provision of a seal of such type, which is competent to restrict leakage of atmospheric gases inward toward a vacuum chamber, with pressure reductions of 10:1 or greater, between the inlet and outlet of a single unit structure.

A further object is the provision of a seal which can be easily opened for threading of a web of material therethrough, and easily closed again to sealed condition.

With these and other objects in view, as will appear in the course of the following description and claims, an illustrative form of practice is shown on the accompanying drawings, in which:

Fig. 1 is a conventionalized showing, partly in upright section, of a vacuum deposition apparatus having a treating chamber to which a web is fed and withdrawn through seals according to this invention, three sealing units being provided at the inlet and outlet points.

Fig. 2 is an upright longitudinal sectional view, substantially on line 22 of Fig. 3, showing the arrangement of parts in a single unit.

Fig. 3 is an upright transverse sectional view, substantially on line 33 of Fig. 2, showing the driving devices and the parts provided for opening the unit for threading the web.

Fig. 4 is an upright section, substantially on line 44 of Fig. 3, showing a drive system.

Fig. 5 is a fragmentary detail section substantially on 1 line 5-5 of Fig. 2.

Fig. 6 is an upright section through another illustrative form of the invention.

Figs. 7a and 7b together comprise an upright section, on a larger scale, through the combined inlet and outlet structure of Fig. 6.

Fig. 8 is a fragmentary conventionalized diagram, on a larger scale, showing the path of a web over rollers.

In these drawings, a web of paper W is provided on a supply roll 10, from which it is withdrawn into the inlet 11 of a first inlet seal unit 12, and thence moves in succession through the second inlet seal unit 13 and the third inlet seal unit 14, and then enters the vacuum deposition chamber 15. After treatment therein, the coated web CW leaves chamber 15 and enters a first outlet seal unit 16, and then passes in turn through the second and third The treating chamber is shown as having an inlet guide roll 21 over which the webmoves and by which it is guided downwardly to the surface of a large coating roll 22. In succession, the web moves from the coating roll 22, a turning roll 23, beneath a second coating roll 24, over a second turning roll 25, beneath a third coating roll 26, over a third turning roll 27, and thence into the first outlet unit 16. This employment of three coating rolls is illustrative of presentation of a surface of the web for acceptance of vaporized metal, such as aluminum, in the treating chamber 15. The coating rolls can be cooled by outlet seal units 17, 18 and is rewound on a take-up reel means known to those skilled in the art; preferably all rolls are positively driven.

Beneath the coating rolls, bus bars 30, 31 extend across the chamber in pairs. Vaporizer elements :E are supported on and receive electrical current from these bus bars: such elements may be of the types shown in my patents, being resistively heated by the current to a temperature above the evaporation point of the deposit material at the low pressure prevailing in the chamber 15. The deposit material may be provided as a filament or wire on reels 32, from which it is drawn by the driven feed rolls 33, and thus delivered into contact with the tops of the heated elements E. The material melts, spreads, and is vaporized to form anatmosphere withinthe chamber 15; and con- .denses .upon the surface of the web W as the latter is supported opposite the elements E by the coating rolls.

The sealing units 12, 13, 14, 16, 17, 18 may be made identical: and one illustrative unit is shown in Figs. 2 and 3.

YA lower housing pan has the bottom 40, the end walls '41, 42.and the side walls 43, 44. The bottom 40 has a'number of transverse ribs 45, above each of which is journaled a lower roller 46, of which six are shownin the illustration. These rollers may have polished steel or .chrome-plated surfaces, and have shaft extensions 47, 48

at their ends. The extensions 47 are journaled to turn in bearings 49 located in the side wall 43 and sealed against .leakage therealong. The extensions 48 pass through bear- :ings 50 in the side wall 44. Plates 51 of inert, low-friction material are provided between the ends of the rollers 46 and the end walls 43, 44 to reduce gas movement around the ends of the rollers: these plates having apertures for .closely receiving the shaft extensions. The end of each extension 48 has gear 52 secured thereto for driving the same. Sheets 53 of a resilient inert material of low -frictional resistance are bent to an L-shape and placed -inithe. grooves between the ribs 45, and individually clamped by angle bars 54 and screws 55 so that the sheets bear against upright faces of the respective ribs in sealing :relation, and also bear under resilient pressure against the "overlying rollers 46, noting that the higher upstreamward pressure serves to hold each sheet in'contact with its .roller. Polyfluoro compounds, such as the commercially available Teflon plastic, are suitable for the plates and :sheets.

The bottom 40 has a flanged hollow extension 57 to whichsuction means may be connected, noting that this "60 has a number of transverse ribs 65, below each of which is journaled an upper roller 66, the number of rollers 66 being illustratively the same as the number of rollers 46 so that the rollers are present in pairs. Each roller 66 has its axis offset or displaced, upstreamward in the illustrated form, relative to the transverse plane through the respective lower roller 46, and is supported out of contact therewith but having its lower generatrix below the level of the upper generatrix of the respective roller 46, so that the web is turned through small arcs in its movement between the rollers of a pair and in its movement toward the next pair. The rollers 66 may be of polished steel or chromium-plated, and have shaft extensions 67, 68 at their ends. These extensions 67, 68 turn in bearings 69, 70, corresponding to the mounting of the rollers 46, and are provided with end sealing plates 71 and gears 72. Sheets 73, corresponding to sheets 53, are

clamped and sealed by the angle bars 74 and screws 75,

.the end walls 41, 61 and 42, 62 are spaced from one another to provide slits 80, 81 for the entrance and exit of the web W; these slits being presented for movement of the web without major contact therewith, noting that external guide rolls 82, 83 (.Fig. 1) may be provided to regularize the position of the web W at entering and web CW at leaving the assembly.

As shown in Fig. 3, the bottom and top walls 40, 60 are extended laterally and connected to side sealing walls 84, 85 which overlap one another (Fig. 5). The walls 85 have grooves 86 for receiving packings 87 correspondingto the so-called O ring; and screws 88 are employed for drawing the walls 84, 85 tightly upon the packings 87. The wall 85 is shown as having a shelf 89 for receiving spacing means 90, such as shims, for engagement by the lower edge of wall 84 and thereby limiting the relative downward movement of the upper structure. This limitation on the relative movement of the structures determines the relative positions of the rollers 46, 66 forming part of the respective structures, and of the vertical dimension of the slits 80, 81 in the illustrative form.

In Figs. 3 and 4, one of the shaft extensions 48 is shown as having a portion 91 passing through a packing gland 92 in the lower or fixed wall 85: whereby a power source external to the evacuated structures can be employed for moving the rollers 46, 66. In Fig. 4, the gears 52, 72 of each pair of rollers 46, 66 are shown as meshing in the operative position of the parts, and idlers 93 are present for transferring motion between successive gears 52. Thus, when .the shaft portion 91 is driven, all of the gears and .rollers turn in the directions shown. by the arrows.

Since the web is not pinched or compressed, but is being fed by the frictional engagement of a large number of rollers turning at an appropriate speed, changes of dimension of the web are compensated by minor slippages at one or another roller, without demanding energy from the web. In the event of major changes in length due to treatment, which might cause undesirable rubbings upon the web surface, speed varying devices may be included in thedrives.

The operation of threading or preparing the structure for operation is simple. The bolts 88 of the units are released, and the upper structures raised; therewith separating gears 72 from gears 52 in each, and leaving the .lower rollers'46 exposed. The chamber 15 has a removable top 15a with a sealing gasket 15b and clamping bolts this top is also removed. The outlet sealing units areopened like the inlet units. The web W is drawn from the:roll 10, passed over the rollers 46 of the inlet units,;threaded over and under the turning and coating rolls in chamber 15, and then passed over the rollers 46 of :the outlet-units. The upper structures of the sealing units and the cover of chamber 15 are then replaced and :sealeduthegears 72 arecngaged with their mates 52 during the closing, any blockage by accumulated back-lash being eliminated by rotation of shaft extension 91 As each upper structure comes to rest upon the adjustable spacing means'90, the sizes of the web slits80, 81, and the-,relation of the rollers inthe pairs 46, 66, are restored.

The structure shown lends itself to employment in multiple .units. InFigs. 2 and 3, the end walls 42 have flanges'projecting beyond the bottom wall 40 and the side walls, and bolts 94 can be passed through these flanges and through the corresponding flanges of the end wall 41 of another'unit, with a sealing gasket 35 between them. 'Supports96 can also be held by such bolts, to mount the unit or group-of units from a frame on the floor as a rigid structure, with the inner stages 14, 16 likewise boltedand sea-ledrelative to the walls of chamber 15.

Similar-assemblies'byflanges, gaskets and bolts can be effected for the upper structures of several units so that these may'be handled .as. a single piece, but with the advantage of disassembly when one unit or part of a unit requires repair.

In operationofan assemblyas inFig. l, the firstinlet and third outlet units 12, 18 are connected at their extensions 57 to conduits 100 which are under evacuation by a rotary mechanical pump: in practice, it was found that, with the outlet 81 sealed, such a pump could reduce the pressure in space 5 8 to 68 millimeters even in the absence of a web. When the inlet slit was reduced so that the pressure in the chamber between the end walls 41, 61 and the rollers 46, 66 was about 34 millimeters absolute, the pressure in chamber 58 was reduced quickly to 208 microns by a 250 liters per second oil sealed pump. The second inlet and outlet units 13, 17 are connected at their extensions 57 to conduits 101 which are under evacuation by a low pressure pump of oil seal type: in practice when units 12 and 13 were thus operated, with the outlet slit 81 of unit 13 sealed, a pressure in the chamber 58 of unit 13 was reduced to 100 microns. The third inlet and first outlet units 14, 16 were closed off and not connected to pumps, so that the pressures in their chambers 58 closely followed the pressure in the treating chamber 15 which illustratively is evacuated by a diffusion pump connected to the exhaust connection 102, to a pressure of, say 0.1 micron. The chamber 58, of each unit, is located at the end thereof nearest the treating chamber 15. When the web W is of paper calipered at 0.003 inch, the slits 80, 81 of the units were adjusted to between 0.008 and 0.012 inch: it being found that the operation was essentially the same within this range. The spacing between adjacent generatrices of the pairs of rollers was adjusted to about 0.007 inch, corresponding to a lap joint of two paper thicknesses and a glue joint 0.001 inch thick. In general, the spacing should be from 2 to 4 times the thickness of paper material, and corresponding allowances for other materials, based on irregularities in thickness thereof and the known thicknesses at joints. The rollers 46, 66 had diameters of about one inch, and were spaced one and a half inches apart in both upper and lower pans. Each upper roller 66 had its axis spaced inch upstreamward from the upright plane of the corresponding lower roller 46. The rotary mechanical evacuation pumping equipment for the first inlet and third outlet units 1'2, 18 drew about 30 liters of free air per second or 60 cubic feet per minute. The other stages or units 13, 17 and 14, 16 were connected as above. It was found that under such conditions, the minor leakages by having the paper width less than the spacing of the plates 51, 71 did not affect the operation; when the paper was 4 inch narrower at each side, i.e. with an equivalent effective slit /2 inch long, the units 12, 18 were reduced to and held at about 25 millimeters absolute pressure at their connections 57; and second stages or units 13, 17 were reduced to 68 microns. The leak effects in the units 14, 16 were negligible, being less than leakages of the chamber 15 itself. When the paper was 1 inch narrower at each side, equivalent to a slit 2 inches long, the outer stages were reduced to and held at 48 millimeters pressure, the middle stages at 50 to 128 microns, and the inner stages were essentially at the intended pressure of the chamber 15.

As another instance of practice, with six pairs of rollers 6'inches long and 1 inch in diameter, the wiper plates 53, 73 were omitted, but the pan walls were located as close to the roller surfaces as possible without contact. The gaps between rollers was 0.009 inch, which was found effective with web thicknesses of 0.004 inch, to permit a splice to pass. The inlet end was sealed except for two ports: a manometer was connected at one port, and a needle valve at the other. The outlet end was connected to an evacuating pump. When a rotary oil pump rated at 100 cubic feet per minute was used, corresponding to the end units 12, 18, and working through the backing lines of other pumps, it was established that its effective pumping speed was 30 liters per second, in the range of to 70 mm. pressure. As the web cannot extend laterally to the ends of the rollers, gaps exist between the roller peripheries at their ends; and most of the leakage can be expected at these gaps. However, the baffling effectof the multiple gaps effectively reduces the flow of 6, air through each. With varying settings of the needle valve, the efiiciency of the seal can be assessed by the manometer readings. v

Empirical equations can be established, as to the total amount of leakage through the unit as a function of the width of the gaps, etc.

The following denominations can be used:

P Pressure at the entry of the seal. P Pressure at the exit of the seal.

G--Widths of the gap between rollers not covered by the web. L -Total leakage through 1st stage. L --Total leakage through 2nd stage. L Leakage through the gap not covered by paper. L -Remainder of the leakage. W-Width of the unit, i.e. width of the rollers.

The amount of leakage is expressed in millimeter litres per second in the first stage and in micron litres per second in the second and third stages. If the leakage and the pumping speed are known at each stage, the prevailing pressure can be obtained by dividing the leakage with the pumping speed. Alternatively, if the leakage is known and the desired pressure is chosen, the leakage divided by this pressure will give the pumping speed necessary for obtaining the selected pressure.

In general the following equation is valid:

FIRST STAGE P =Atmospheric pressure 760 mm. P =25 mm. if the paper extends from edge to edge of the rollers or G=0. P =73 mm. if there was no paper in the sealing unit and G=6.

The results of a number of measurements with varying measurements for G established the validity of the following equation in the range of P =25 to 75 mm:

L =750+240 G mm. l./second (1) In order to be able to calculate the leakage through a seal of any chosen width and the necessary pumping speed, it should be known how L is dependent on the width of the seal. This is difficult because L is the sum of a number of different small leakages, some of which are independent of the size of the seal. However, it is obvious the most unfavorable assumption that L is proportional to the width of the seal. By making this assumption in the following calculations, a fairly large safety factor is introduced. I

L, for a 6" wide seal was found to be 750, thus for a seal the width of which is W Le: 750W The readings corresponding to a second stage such as units 14, 17, a Kinney KMB-1200 lobe pump was used, also pumping through the various lines; and its pumping weapon 7 ratewas'es'tablished' as 240 litersper second in. the'100- micron range.

In the second stage P equals less than atmospheric pressure. From Equation 2, it can be seen that it is practical to reach an exit pressure, P =25 to 75 mm. in the first stage and this will be the entry pressure, P; for the second stage. There is a difference in the type of equation which governs the leakage through the second stage, because in the first stage P is always equal to the atmospheric pressure while in the second stage P depends on the pumping speed and the total leakage through the first stage. The leakage through the second stage is dependent on P Actual measurements were made with the experimental unit in such a way that the fiow into the seal was regulated by the needle valve and P and P measured. From these data the following empirical equation was established which corresponds fairly well with the measured figures in the range of 25 to 75 mm. for P Example] W=24 G=2 Width of web 22" First stage P =Atmospheric pressure L =125 24'+240 2=3,480 mm. L/second A pumping speed of 100 l./ second at the exit end of the first stage will give:

3,480 P 100 ca. 35 mm.

SECOND STAGE P =35 mm. L .=40 24(1.55 3531+69) =88,560 micron l./ second A pumping speed of 500 l./second at the exit end of the second stage will give:

The following considerations establish that in the third stage no pumping station is needed, but that the third sealing unit can discharge straight into the evaporating chamber. The pressure between the exits of the first and second stages is reduced by a factor of 200 (from 35 mm. to 177 microns) with a pumping speed of 500 l./second. When P equals 5 mm., the measured P and 24 microns with a pumping speed of 240 l./secoud, thus reduced again by a factor of 200. However, P will only be 177 microns, and the pressure reduction at this entry pressure will be considerably higher than at P =5 mm. Even neglecting this difference and assuming a ratio of 1 to 200, P will be only about 0.9 micron and the leakage rate 216 micron liters per second (abbreviated, l./sec.). The leakage rate in the 24" unit might be up to three times this figure, i.e. ca. 600 micron l./sec. Assuming a pumping system for the vaporizer which will have a pumping speed of 5,000 l./sec. at 1 micron, which is equivalent to a leakage rate of 5,000 micron l./sec., only about 12% of the pumping speed will be used to take care of the leakage through the sealing unit. This is considerably less than needed to take care of the entrapped air in a master roll-of paper or plastic film loaded in a non-continuous machine.

The conclusion is that for a 24 wide continuous vaporizing' machine, the pumping speed required for the seals-is as follows:

L/sec. in a pressure range of 25 to 72 microns on both sides of the machine, and 500' l./sec. ina pressure range of- 100 to 300 microns on both sides of the machine.

Taking into consideration the losses in the pumping lines, that means 2 rotary oil pumps of 150 l./sec. capacity each, and- 2 lobe pumps of 750 L/sec. capacity each.

It is possible, to design the sealing units in such a way that the webenters and leaves the system through the same sealing units. This measure reduces the. leakage through the seals. Instead of having two rows consisting of two rollers each, such a seal will have one row of three rollers. A considerable part of the leakage will be reduced to of its original value. sealed by two rows of Teflon blades instead of four rows. This will reduce another sizeable part of the leakage to /2' of the calculated value. assumed that the total leakage will be reduced to of the calculated value and in such a system two pumps will be needed, one with 200 l./sec; pumping speed at 25 to 75 microns and another one with 1,000 l./sec. pumping speed at 100 to 300' microns pressure. This pumping can easily be provided by a 400 c.f.m. rolary oil pump and two 1000 c.f.m. rotary lobe pumps. The latter two can be used simultaneously for backing of the vapor pumps Working on the vaporizing chamber.

Example 2 Similar calculations show that a 64" wide machine requires the following pumping speeds:

L./sec. First stage 500 Second stage 2000.

For the first stage, two rotary oil pumps of'about 500 c.f.m. capacity would be adequate. For the second stage, two large lobe pumps with a pumping speed of 1,000 l./sec. each are used. The second stage pump would, at the same time, serve as a backing pump for the vapor pumps working on the evaporating chamber.

This form is shown in Figs. 6 and 7, where the inlet and outlet of the web is accomlished by a composite guidingand sealing structure having three sets of rollers.

The fresh web W is fed from a supply roller over a guide roller 111 and into the sealing structure by a slit 112. After passing through the sealing structure, the web W is guided downwardly through an opening forming communication between the sealing structure and the interior of the treating chamber, and past a turning roll 114 and thence onto the surface of a large cooled drum in the treating chamber 115. This drum 116 is driven and the web is coated by condensation of vapor coming from the vaporizer elements E. The coated web leaves the drum near its top and passes the turning roll 117 and re-enters the sealing structure. From the sealing structure the coated web CW passes through a slit 113, a guide roll 118 and is re-wound on a take-up reel 119.

The sealing structure has a bottom pan 120 with end walls 121, 122 and side walls 123. Along its length are spaced downwardly extending hollow projections 125, 126 which may respectively be connected to evacuating means such as a rotary pump and a low pressure pump, as described above for the connections 100 and 101. Rollers 127, 128, 129 in three series are journalled in the walls 123 of the bottom pan 120, and can be sealed, mounted and driven as described above. An intermediate frame 130 has peripheral Walls; and three series of rollers 131, 132, 133 are journalled therein, and can be driven with the rollers 127, 128, 129 as shown in Fig. 4. A top pan 135 has end and side walls, and journal bearingsfor The rollers can be three series of rollers 136, 137,138, which are positively driven in like manner. Q

The rollers of the pans 120, 135 and the intermediate frame 130 thus form three sets: (1) rollers 127, 131, 136 (Fig. 7b) between the inlet-outlet end of the structure and the chamber 139 above the first suction connection 125; (2) rollers 128, 132, 137 (Fig. 7b) between the chamber 139 and a chamber 140 above the second suction connection 126; and (3) rollers 1'29, 133, 138 (Fig. 7a) between the chamber 140 and end chamber 141 located at the communicating opening with the treating chamber 115. In each of these sets, the superimposed rollers are staggeredrelative to the rollers next below, so that the web is turned through small arcs at each contact with a roller and thus forms a seal as with the fi-rst form. The rollers journaled in the top pan 135 are shown as turning counterclockwise, and the rollers journaled in the frame 130 as turning clockwise; that is, their surfaces move in the same direction as the entering web W which passes between them. Likewise the clockwise direction of the rollers on the frame and the counterclockwise direction of the rollers on the pan 120 causes them to turn in the directions of outward movement of the coated Web CW which is between them. The rollers are mounted so that they do not contact with one another, nor do they press against a web of the operating thickness, including jointing laps, so that the web is at any time pinched between pairs of rollers. Thus each set of rollers provides a series of seals by multiple contacts with the web as before.v In this form, each of the rollers 127, 128, 129 are located with their peripheries close to the adjacent wall of the pan 120; and each of the rollers 136, 137, 138 close to the adjacent wall of the pan 135. With ground and polished surfaces, this spacing can be less than 0.001 inch: and a corresponding spacing can be attained at the ends of the rollers. Thus, in this form, the plates 51,

'71 and the blades 53, 73 can be omitted.

The side seals and driving means can be as shown for the first form.

In each form, the web departs from its general direction of advancement and takes a zigzag course by short arcs of contact with the successive rollers, thus acting to provide seals between the sub-chambers at the upstreamward and downstreamward sides of each roller. The rollers at each side of the web are staggered relative to one another, and are preferably spaced about 2 /2 to 6 times the normal thickness of the web material.

Fig. 8 shows, on a greatly enlarged scale, the path of a web of material between rollers which contact it at its opposite sides. An upper roller 145 is shown (corre sponding to an upper roller 136, 137 or 138 in Figs. 7a and 7b; or with reversal of the web movement to an intermediate roller 131, 132 or 133 of Figs. 7a and 7b, or an upper roller 66 in Fig. 2) as one member of a roller pair with a lower roller 146 (corresponding to an intermediate roller 131, 132 or 133 in Figs. 7a and 7b; or with reversal of web movement to a lower roller 127, 128 or 129 in Figs. 7a and 7b, or a lower roller 46 in Fig. 2). A second upper roller 147 is shown, for designating the path of the web as it leaves roller 146. The web W encounters the peripheral surface of the upper roller 145 and engages it for the are 151, is therewith deflected from its general direction of movement by a corresponding angle, and then moves along the tangent to the peripheral surfaces of roller 145 and of lower roller 146 for the distance 152. The web W engages the roller 146 for the are 153 and is deflected to move along the tangent to the peripheral surfaces of roller 146 and the next succeeding upper roller 147 for a distance 154, and then engages the roller 147 for an arc. The peripheral surface of the roller 146 extends beyond the tangent plane of rollers 145,

' 147, this plane being indicated by the line 155 in Fig. 8.

The peripheral surfaces of rollers 145, 146, considered as a pair comprising one roller above the web and one roller below the web, are separated by the distance 156 measured along the line 157 joining the axes of the.

rollers of this pair: this distance being from 2% to 6 times the thickness of the Web of material. This same relationship is provided between the pairs of rollers in Fig. 2, and other pairs of rollers in Figs. 7a and 7b.

It will be understood that the above empirical equations have been established on the basis of experimental results obtained with a particular experimental sealing unit, and the numerical values obviously will differ with other seals, depending on the accuracy of the workmanship, tolerances in the clearances, effectiveness of O-ring seals, and other factors. It should also be understood that these equations are valid only within the pressure ranges for P of the order stated above.

It is obvious that the illustrative form is not restrictive,

but that the invention may be employed in many ways within the scope of the appended claims.

What is claimed is:

1. A sealing structure for the passage of flexible materials between regions at differing pressures, of gas therein, comprising a housing, rollers journalled in the housing to turn about parallel axes, a first set of said rollers having their axes at one side of the path of the material and being effective to engage the material at the said one side thereof and a second set of said rollers having their axes at the other side of the path of the material and being effective to engage the material at said other side thereof, the rollers being staggered so that the axial plane of each roller which is normal to the general direction of movement of the material is not coincident with the like axial plane of any other roller, said housing including sealing means for restricting flow of a said gas around the ends of the rollers and around the peripheral parts of the rollers remote from the path of the material, the peripheral surface of each roller of said one set extending beyond a tangent plane of the peripheral parts of the adjacent rollers of the second set, said tangent plane being that which is nearest to the axis of the said roller of said one set so that the material contacts a roller at one side for an arc and then passes on a tangent to contact a roller at the other side for an arc and therewith performs a zig-zag course upon and between the said rollers whereby the material itself is effective to restrict passage of gas between a pair of successively contacted rollers, each roller having its peripheral surface spaced from the peripheral surface of the adjacent roller of said pair and located at the other side of the material by a distance of two and one-half to six times the thickness of the material.

2. A structure as in claim 1, in which the rollers are positively driven, with the rollers turning in such directions that at the arc of contact they move in the direction of the material.

3. A structure as in claim 1, in which the sealing means include blades secured and sealed to the housing and engaging the peripheries of respective rollers.

4. A structure as in claim 3, in which the blades are located to engage the peripheries of the rollers at points exposed to the greater gas pressure.

5. A sealing structure as in claim 1, in which the housing is in sections, with each section supporting the rollers at one side of the material, whereby upon separating the sections, the material may be threaded by introducing it against the rollers of one section, and then bringing the rollers of the other section against the other surface of the material, and means for securing and sealing the sections together.

6. A structure as in claim 5, including means for limiting the engagement of the sections with one another whereby to determine the position of the rollers on one section relative to the rollers on the other section.

7. A sealing structure for the passage of a flexible web of material between regions at differing gas pressures, comprising a housing of divided sections, rollers in each section, a first set of said rollers having their axes at one side of the web and being :elfective'to engage said: side ofztheuweb and a second set of saidrollers having their axes at the other side of .the web and being effective to engage said other side of the web, said housing including sealing means for restricting gas flow around the ends of the rollers and .around the peripheral parts of the rollers remote from the path of the material, and journal means on the sections for supporting the rollers to turn about :parallel axes, said journal means being effective for .presenting the rollers at each side of the material staggered relative tov the adjacent rollers at the other side and with the peripheral surface of each roller of said oneset extending beyond a tangent plane of the peripheral parts of the adjacent rollers .of. the second set, said tangent plane being that which is nearest to the axis of said roller of said one set so that the material contacts a roller at one side 'foran arc and then passes .on a tangent to contact a roller at the other side for an arc and there- -withlpertormsia zig-zag course upon and between the said rollers-:whereby the material itself is effective to restrict passage of gas between-a pair of successively contacted rollers, each roller having its peripheral surface spaced from the peripheral surface of the adjacent roller of said *pair and located at the other side of the material by a distance of two and one-half to six times the thickness of the material.

'8. A structure as in claim 7, in which the sections each include extension walls providing a lateral chamber, and in which the rollers have end shafts extending into said chamber, gears 'on each shaft with the gear on a shaft 'from a roller in one section in mesh with the gear on a 'roller in the other section.

9. A structure as in claim 8, in which one said shaft extends outside the chamber, and sealing means are provided between the sections around said lateral chamber.

10. A structure as in claim 8, in which the gears of rollers at one side of the material are connected through idlers whereby all rollers at one side of the material are 12 driven in one direction and all rollers at the other side are driven in the other direction.

11. Astructure as in claim 7, in which the sections are composed of separable'elements each having a said roller therein, and including flanged end walls on the elements whereby a number of the said elements can be connected end-to-end and handled as a unit section, connecting means for said'flanged end walls, and means for limiting the approach of the end walls of cooperating elements whereby to provide end slits through which the material can enter and leave the assembly of the said cooperating elements.

12. A'structureas inclaim 11, including a support securedito the end wall flange of a said element.

13. A structure as in claim 7, in which there are two sections having overlapping side walls, and sealing means between the sectionsv located at the overlap thereof.

14. A structure as in claim 7, in which there are three sections each having rollers journaled therein, with means for rotating the whereof the outermost sections in .one direction and the rollers of the intermediate section in the opposite direction, the flexible web being advanced from a region of higher pressure toward a region of lower pressure between the rollers of one outer section and the rollers of the intermediate section, said web being returned from the region of lower-pressure to the region of higher pressure between the rollers of the intermediate section and the rollers of the other outer section.

15. A structure as in claim 7, in which the housing has a chamber at the end having the lower pressure, and an evacuating means is connectedlto the housing incommunication with said chamber.

ReferencesCitedtin the file of this patent UNITED STATES PATENTS 2,382,432 McManus et al Aug. 14, 1945 2,384,500 Stoll Sept. 11, 1945 2,815,307 'Beck Dec. 3, 1957 

